Police in France have captured the suspected military leader of the armed Basque separatist group Eta, Jurdan Martitegi. The move dealt a further blow to the group, which is reported to be considering a return to peace talks.

The arrest of 28-year-old Martitegi in Perpignan, south-western France, came only four months after he allegedly took over responsibility for Eta's campaign of bomb and pistol attacks in Spain.

He was detained along with two other Eta members, and his arrest was considered further proof of the group's decline during the last two years. He was the fourth alleged military leader of Eta to have been captured over the past year.

Martitegi was arrested after a joint operation by Spanish and French police, who tailed another alleged Eta member from his home in Spain to a meeting with the group's military leader in Perpignan.

The arrests in France triggered a police operation in northern Spain which saw six more people detained yesterday and early this morning.

Eta's previous military leader, Aitzol Iriondo, was arrested in France in December, and Iriondo's predecessor, Garikoitz Apiazu, was caught only three weeks before that. Another military leader, Javier López Peña, was arrested last May.

The group's military leaders are nominally in charge of running the group's armed units and organising bomb and pistol attacks.

Their weight in Eta's political structure, which decides on strategy, has varied considerably over the four decades of its history.

The four military leaders captured over the last year are believed to have led a hardline faction within the group that was responsible for calling off the last ceasefire.

That decision ended months of secret negotiations with the socialist government of José Luis Rodríguez Zapatero, the Spanish prime minister, over an end to Eta's violence.

Analysts speculated that the arrest of Martitegi, which followed the detention last week of an Eta member caught in an armoury in the southern French town of Mézières-en-Brenne, would shift power within Eta away from the hardliners.

Eta prisoners in Spanish jails have been increasingly critical of the current leadership in recent years. Some have called for a negotiated end to what has become a largely ineffectual terrorist campaign.

The arrests coincided with a report in El País newspaper that Josu Urrutikoetxea, a veteran Eta member thought to be in favour of a return to peace talks, may have recently returned to the group's political leadership.

Urrutikoetxea, alias Josu Ternera, was reportedly one of the negotiators who took part in talks with government representatives during the ceasefire.

Zapatero's government, having been caught out by Eta's previous return to violence, is now less inclined to talk.

During the last ceasefire, the government was ready to discuss the future of Eta prisoners now in Spanish jails, but was unwilling to concede to any of Eta's political demands.

Zapatero's socialists are poised to take control of the Basque regional government, which has been in the hands of moderate Basque nationalists for the past 29 years, in the next few weeks.

The new regional government comes after the March elections in the Basque country which saw the nationalists lose their grip on power.

Parties deemed to be fronts for Eta, which usually win at least 10% of the Basque vote, were banned from those elections, meaning they no longer have any say in how Spain's northern Basque country is governed.

A definitive end to Eta's violence would see those bans dropped.

Eta last week contacted the Basque newspaper Gara saying it would make the new regional government ‑ which is due to be led by socialist Patxi López ‑ one of its priority targets.